Since the introduction of automatic transmissions, hydrodynamic converters have formed the link between a drive engine and the actual transmission. A converter, on the one hand, enables comfortable, jerk-free starting by virtue of slippage and at the same time damps speed irregularities of the combustion engine. On the other hand, the torque magnification inherent in its principle provides a large starting torque.
According to the present state of the art, a hydrodynamic converter consists of a pump impeller, a turbine rotor, the reaction element (reactor, stator) and the oil required for torque transmission.
The pump impeller, which is driven by the engine, moves the oil in a cyclic flow. This oil flow impinges on the turbine rotor and is there deflected in the flow direction.
In the hub area, the oil leaves the turbine and passes to the reaction element (stator), where it is again deflected and so led back to the pump impeller in the appropriate flow direction.
Owing to the deflection, a torque is produced on the stator, whose reaction moment increases the turbine torque. The ratio of turbine torque to pump torque is denoted as the torque boost. The larger the rotation speed difference between the pump and turbine, the larger is the torque boost which is maximum when the turbine is at rest. As the turbine speed increases, the torque boost decreases. If the turbine speed reaches around 85% of the pump speed, the torque boost=1, i.e., the turbine and pump torques are equal.
In this condition, the stator, which is supported on the transmission housing via the freewheel and the reactor shaft, runs freely in the flow and the freewheel is overrolled. From this point onwards, the converter operates as a pure flow coupling. During conversion the stator is stationary and is supported on the housing via the freewheel.
From the prior art converters are known, which comprise a converter bridging clutch and a primary clutch, the primary clutch (PK) being arranged between the engine and the converter and the converter bridging clutch between the engine and the transmission.
Such converters are usually provided for vehicles which work at very low speeds, but which can also drive at high speeds. For example, within the scope of DE 195 21 458 A1 a converter with a converter bridging clutch and a primary clutch is described. According to this prior art, the converter bridging clutch and the primary clutch are each provided with their own pressure supply and their own valve unit.
The purpose of the present invention is to provide a hydrodynamic converter comprising a converter bridging clutch and a primary clutch, which is of compact structure with a small number of components. Furthermore, a method for controlling and/or regulating the primary and converter bridging clutches of the hydrodynamic converter according to the invention is proposed.